The purpose of these experiments is to improve the technique of surface and perfusion hypothermia with circulatory arrest in order that congenital heart lesions may be totally corrected in newborns. A second objective is to study alterations in pulmonary and cerebral function and morphology and to study means by which observed changes can be prevented or controlled. Selection and design of equipment and alteration of the perfusate will reduce circulating emboli, minimize blood trauma, and reduce alterations in the microcirculation. Measurements of lung water, gas volumes, mechanics and vascular changes will be made and the effect of continuous positive airway pressure on these measurements will be studied. The distribution of blood flow and measurements of organ oxygen consumption and vascular resistance will be made during cooling and rewarming.